DIGITAL VIEWING DEVICE

Abstract

The invention relates to a digital viewing device, comprising at least one camera module, consisting of an objective (2) having a focal length fobj and an image sensor (3) having an image diagonal d.sub.Sensor, and at least one electronic viewfinder, consisting of an eyepiece (9) having a focal length f.sub.Oku, an image processor (5), a power supply (7) and an electronic display (10) having an image diagonal y.sub.Display, characterised in that to correct distortion of the image generated on the display the image processor contains at least one computer program with distortion correction algorithms and the computer program can be switched on by means of an activating element (6).

Claims

1. A digital observation apparatus comprising: at least one camera module, comprising an objective with a focal length f.sub.Obj and an image sensor having an imaging diagonal measurement d.sub.Sensor; and at least one electronic viewfinder, comprising an eyepiece having a focal length f.sub.Oku, an image processor, a power supply and an electronic display having an imaging diagonal measurement d.sub.Display; wherein the image processor comprises a computer program with a distortion-correction-algorithm for correcting a distortion on the image displayed on the display; and the computer program is activatable via an actuation element.

2. The digital observation apparatus of claim 1, wherein the distortion correction is continuously adjustable via the actuation element.

3. The digital observation apparatus of claim 1, wherein the distortion correction is adjustable in discrete levels via the actuation element.

4. The digital observation apparatus of claim 1, wherein a manual adjustment of the actuation element is provided, which is provided as an actuating element on the outside of the housing.

5. The digital observation apparatus of claim 1, wherein an automatic setting is provided for the actuation element.

6. The digital observation apparatus of claim 5, wherein a motion sensor is allocated to the image processor and the automatic adjustment is performed dependent on the signals from the motion sensor.

7. The digital observation apparatus of claim 6, wherein an image memory card is allocated to the image processor and the respective adjusted distortion corrections are storable separately.

8. The digital observation apparatus of claim 7, wherein the digital observation apparatus is selected from the group consisting of a digital telescope, digital binoculars, a microscope and an endoscope.

9. Digital telescope according to claim 8, wherein in case of binoculars the distortion correction is identical between the two binocular viewing paths.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Embodiments are shown schematically in the drawings and are described in the following. In the drawings show:

[0019] FIG. 1 digital telescope having a switch,

[0020] FIG. 2 digital telescope with a switch and a motion sensor, and

[0021] FIG. 3 a diagram showing curves for a variety of distortion parameters k.

DETAILED DESCRIPTION OF THE DRAWINGS

[0022] The telescopes shown in FIGS. 1 and 2 are monocular and are shown in a side view. The optical and electronic elements are mounted inside a housing 1.

[0023] The front module comprises an objective 2 having a focal length f.sub.Obj and an image sensor 3. The objective 2 captures the imaging beams 4 from the object space at a viewing angle α of the objective and images these onto the image sensor 3.

[0024] The signals captured by the image sensor 3 are transmitted to an image processor 5. Various operational modes of the image processor 5 can be turned on by an actuation element 6 that is accessible from a location outside of the housing 1.

[0025] The processor comprises an energy supply 7 that is likewise accessible from the outside. This may for example be a lockable battery compartment.

[0026] At the end of the housing 1 that is facing the observer having the eye 8 an eyepiece 9 having a focal length f.sub.Oku and a display 10 having an image height y.sub.Display are positioned. The display 10 is observed by the eye 8 under a subjective view angle α′.

[0027] According to the arrangement shown in FIG. 2, a motion sensor 11 is additionally provided and connected with the image processor 5. Based on signals from the image sensor 11 a variety of distortion corrections can be automatically adapted to the current operation of the telescopes.

[0028] Further, an image memory card (SD-card) 12 is connected to the image processor 5.

[0029] The distortion can generally depend on the view angle α of the objective, the distortion parameter k, and the magnification Γ and may be described by the following formula:

[00001]$\mathrm{Dist}\left(\alpha ,k,\Gamma \right)=\frac{\tan \left(\frac{\arctan \left(\Gamma .Math.\tan \left(k.Math.\alpha \right)\right)}{k}\right)}{\Gamma .Math.\tan \left(\alpha \right)}-1$

[0030] Herein, the magnification of the digital telescope Γ is calculated as follows:

[00002]$\Gamma =\frac{f_{\mathrm{Obj}}}{f_{\mathrm{Oku}}}.Math.\frac{d_{\mathrm{Display}}}{d_{\mathrm{Sensor}}}$

[0031] wherein d.sub.Display is the diagonal measurement of the screen and d.sub.Sensor is the diagonal measurement of the sensor.

[0032] As a good approximation, the distortion depends only on the subjective view angle α′ and the distortion parameter k, not on the magnification Γ.

[00003]$\mathrm{Dist}\left({\alpha }^{\prime },k\right)=\frac{k.Math.\tan \left({\alpha }^{\prime }\right)}{\tan (k.Math.\arctan \left(\tan \left({\alpha }^{\prime }\right)\right)}-1$

[0033] For an eyepiece by which the image of the digital display is viewed the distortion can be calculated in a good approximation based on the focal length of the eyepiece f.sub.Oku, the image height y.sub.Display of the display, as well as the distortion parameter k.

[00004]$\mathrm{Dist}\left(f_{\mathrm{Oku}},y_{\mathrm{Display}},k\right)=\frac{k.Math.\frac{y_{\mathrm{Display}}}{f_{\mathrm{Oku}}}}{\tan \left(k.Math.\arctan \left(\frac{y_{\mathrm{Display}}}{f_{\mathrm{Oku}}}\right)\right)}-1$

[0034] A non-corrected image point on the display at a distance r.sub.0 from the middle of the display is displayed according to the invention at a distortion correction Dist at a distance of r=r.sub.0.Math.(1+Dist) from the middle of the display.

[0035] In a practical implementation, several curves for k are stored as a table of values for k in the memory processor 5 (e.g. 0.0, 0.25, 0.5, 0.75 and 1.0) and can be provided by the processor 5 and the image can then be displayed on the display 10 at the calculated distortion.

[0036] As an alternative, as an approximation, the distortion can be calculated as a simple function of k and

[00005]$\frac{y_{\mathrm{Display}}}{f_{\mathrm{Oku}}}$

and may then be calculated for example as

[00006]$\mathrm{Dist}\left(f_{\mathrm{Oku}},y_{\mathrm{Display}},k\right)=\mathrm{coeff}.Math.\left(1-k^2\right).Math.{\left(\frac{y_{\mathrm{Display}}}{f_{\mathrm{Oku}}}\right)}^2$

[0037] For example, this correlation is sufficiently accurate at coeff=0.29 up to y.sub.Display/f.sub.Oku=0.7, which correlates to half of the subjective view angle α′ of 35° of the eyepiece. Consequently, a total view angle of (2.Math.α′) of 70° results.

[0038] The distortion adjusted for the display 10 should always extend over the entire image area and should be oriented based on the entire shows and curved for avoiding unnatural image gradients.

[0039] The distortion of the optics of the objective may already be corrected by the processor 5 correlating to the sensor 3. If this is not the case the distortion correction as described above needs to be offset by calculation so that the image shown on the display comprises the desired distortion.

[0040] Also the distortion of the eyepiece optics needs to be offset by calculation with the above described distortion correction so that the image shown on the display 10 as viewed by the observer is observed at the desired distortion. A pre-stored table or an approximation function for the control of the distortion correction are then adapted accordingly.

[0041] If the focal length of the objective 2 is zoomable and consequently the magnification of the apparatus can be changed, this does in and of itself not have an influence on the above described distortion correction since it is independent of the magnification. Only an influence on the distortion of the optics of the objective based on the zoom is taken into consideration.

[0042] This is different if the focal length of the eyepiece 9 is zoomable and consequently the magnification of the apparatus can be varied. Since the distortion correction depends on the focal length of the eyepiece 9 a change for instance in the electronic scanning of a mechanical control curve, which is not further shown in the drawings, and its correlation to the set focal length is taken into consideration.

[0043] Since some observers also prefer a distortion correction while observing constantly in one direction for having a more natural viewing perception two values for the distortion parameter k may be provided, namely one for observing constantly in one direction and one for observing while panning. As an option, the user can also choose to set both values as identical values.

[0044] The diagram shown in FIG. 3 shows as an example curves for k=0.0001 through 1.0, wherein the distortion in % is provided on the X-axis and the values for arctan(y.sub.Display/f.sub.Oku) are provided on the Y-axis. At the right edge of the curve curving parameters are shown for k=0.0 (top) through 1.0 (bottom). K=1.0 correlates to a curve extending along the y-axis. For k values approaching 0 curves result which extend from the origin of coordinates to a value of 35 along the y-axis trending progressively in direction of the 15% value on the x-axis.

[0045] The control options as described above are also of interest for additional apparatuses having an electronic viewfinder (EVF), for example for endoscopes or for microscopes. In case of endoscopes, viewing is often done by movement through an organ. In this case, it is helpful to avoid the globe effect. When during the examination geometries are measured and calculated, the distortion may be considered in the used measuring algorithm. Also in some applications for microscopes the globe effect is disturbing, for example when scanning an object.

LIST OF REFERENCE NUMERALS

[0046] 1 housing [0047] 2 objective [0048] 3 image sensor [0049] 4 imaging beams at the objective [0050] image processor [0051] 6 actuation element [0052] 7 power supply [0053] 8 eye [0054] 9 eyepiece [0055] 10 display [0056] 11 image sensor [0057] 12 memory card [0058] α half of the viewing angle of the objective [0059] α′ half of the viewing angle of the observer [0060] Γ magnification of the telescope [0061] k distortion parameter